Various electro-optical readers have previously been developed for reading both one- and two-dimensional bar code symbols appearing on a label, or on a surface of a target. The bar code symbol itself is a coded pattern of indicia. Generally, the readers electro-optically transform graphic indicia of the symbols into electrical signals, which are decoded into alphanumeric characters. The resulting characters describe the target and/or some characteristic of the target with which the symbol is associated. Such characters typically comprise input data to a data processing system for applications in point-of-sale processing, inventory control, article tracking and the like.
Moving beam electro-optical readers have been disclosed, for example, in U.S. Pat. No. 4,251,798; No. 4,369,361; No. 4,387,297; No. 4,409,470; No. 4,760,248; and No. 4,896,026. Typically, a laser beam is directed toward a one- or two-dimensional coded symbol. The laser beam is repetitively swept in a scan line or a series of scan lines across the symbol for reflection therefrom by means of motion of a scanning component, such as a scan mirror. A sensor or photodetector, together with a collection lens assembly comprised of one or more lenses, capture and detect laser light reflected or scattered from the symbol. The sensor generates an electrical analog signal indicative of the laser light returning from the symbol. Electronic control circuitry and software decode the analog signal into a digital representation of the data represented by the symbol that has been scanned. The binary data may then be converted into the alphanumeric characters represented by the symbol. The data may be decoded locally or sent to, and decoded in, a remote host for subsequent information retrieval.
Both one- and two-dimensional symbols can also be read by employing imaging readers having a solid-state imager which includes a one- or two-dimensional array of cells or photosensors which correspond to image elements or pixels in a field of view of the imager. A collection lens assembly comprised of one or more lenses captures either ambient light reflected or scattered from the symbol in the case of a brightly lit environment, or illumination light directed at the symbol for reflection and scattering therefrom in the case of a dimly lit environment in response to actuation of a trigger. The captured light is directed to the imager, which may advantageously be a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and includes associated circuits for producing electronic signals indicative of the captured light and corresponding to a one- or two-dimensional array of pixel information over the field of view. The electronic signals may be processed by a microprocessor either locally or sent to, and processed in, a remote host to read the symbol from the captured light.
As advantageous as such moving beam and imaging readers are in capturing data as stand-alone data capture systems, such a reader can be a relatively large and expensive component in assembly and manufacture, especially if it is installed in an apparatus in which the reader is a subsystem. For example, a coffee maker is an example of an apparatus in which the reader may be installed to read symbols on packets of coffee in order to instruct the coffee maker how to brew a particular packet. The reader is a subsidiary system in the coffee maker and, therefore, its design must be optimized such that its size, as well as its assembly and manufacturing costs, are minimized.
It is known to use an adhesive to adhere a collection lens, as described above, in a fixed position in front of a light sensor of the reader. However, the collection lens must be optically and physically positioned with a high degree of accuracy relative to the sensor. This is difficult to achieve economically when an adhesive is employed. A manufacturer is not likely to use an uneconomic, large-sized reader, especially in an apparatus with little room to spare.